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Doklady Chemistry, Vol. 391, Nos. 4–6, 2003, pp. 225–227. Translated from Doklady Akademii Nauk, Vol. 391, No. 6, 2003, pp. 791–793.Original Russian Text Copyright © 2003 by Ganiev, Berlin, Malyukova, Fomin.

We previously [1] showed that resonant vibrationtreatment of polymer composites containing the liquidphase enhances chemical and phase transformations inthese multiphase systems.

The dynamic behavior of multiphase systems wasstudied throughout the composition range: from low-viscosity media, such as emulsions, latexes, dispersionsof fillers and pigments in water and organic solvents(paints and varnishes, etc.), to high-viscosity mixturesof plastics, rubbers, and rubbers with plastics (resinmixtures). This study revealed that the properties of allof these materials are due to their multilevel heteroge-neity, which requires one to enhance the efficiency ofmixing of components. According to Rehbinder’s clas-sification, most of these systems are unstable lyophobiccolloidal systems, whose production requires one toovercome intermolecular forces and is accompanied bythe accumulation of free surface energy during disper-sion as the external mechanical work is done. The prop-erties of such disperse systems, including their resis-tance to aggregation, phase stability, polydispersity,and rheological characteristics, are largely governed bythe size of the dispersed particles. The character of mix-ing and dispersion can be different. As is known, mix-ing of high-viscosity media takes place in a laminarmode, whereas treatment of composites containing theliquid phase is usually performed in a turbulent mode.The set of the properties of polymer composites isdetermined by their chemical and phase composition,the particle size, the distribution of components, andthe supramolecular organization; the efficiency of mix-ing is controlled by the action on these parameters. Inthis context, it seems reasonable to use wave technol-ogy based on excitation of nonlinear vibrations in amultiphase medium, which considerably enhancesmass-transfer processes [1].

In this paper, we considered vibration treatment ofmultiphase polymer systems of medium viscosity (ofdynamic viscosity 10

–1

–10

2

(N s)/m

2

(10–10

3

P)): latexcomposites with powder fillers (such as zeolites and

activated carbon), suspensions (pastes) of chalk andtitanium dioxide in water, and paints (latex paint,primer paint, and nitrocellulose enamels). A wave fieldwas produced with a VEDS-400A shake table and asimilar setup (a platform vibrator) vibrating at a fixedfrequency of 50 Hz. The vibration amplitude corre-sponded to accelerations of 20

–

25

g

. It was assumedthat these setups would enable us to create two-loop cir-culation and three-dimensional flow, which favor effi-cient mixing.

The figure and Tables 1 and 2 show that wave treat-ment based on excitation of nonlinear vibrations inmultiphase media being treated decreases the particlesize in such systems, increases their homogeneity andresistance to aggregation, and improves their physico-chemical properties. As already noted, the most opti-mum mode is the resonant mode, which ensures disper-sion and turbulent mixing with the minimum energyconsumption [1]. The increase in the resistance toaggregation of disperse systems in which emulsifiers(stabilizers) are fine-particle powders of chalk, clay,zeolites, and so on, can be explained by the adsorptioninteraction between powder particles, which gather atthe interface to form a spatial structure (barrier) pre-venting coalescence of dispersed-phase particles (thestructural-mechanical stabilization factor). Earlier [2],we obtained the expression for the particle size as afunction of the energy dissipation rate in vibrationtreatment of a multiphase system. It was demonstratedthat the critical size of dispersed-liquid drops in emul-sions according to the Kolmogorov–Hinze theory is

governed by the Weber number: We = where

σ

is the surface tension,

δ

is the difference in the veloc-ities of the dispersion medium on the opposite sides ofthe drop,

ρ

is the density of the dispersion medium, and

d

is the drop size. Estimation of the particle size in amotor oil–water emulsion (and also in a motor oil–water–chalk emulsion) showed that wave treatment ona setup with a hydrodynamic generator for 5–10 mingives rise to an emulsion of particles of size 1–3

µ

m [3].Previously [5], mechanisms of excitation of acousticvibrations with a swirl-type hydrodynamic generator[4] were considered, a mathematical model was con-structed to calculate the hydrodynamic resistance andthe velocity field in the formation of a cavitation

ρδ2dσ

-------- 1≥ ,

CHEMICALTECHNOLOGY

Some Features of the Design of Properties of Polymer Composites under Wave Treatment

Academician

R. F. Ganiev*,

Academician

A. A. Berlin**, E. B. Malyukova*, and V. N. Fomin*

Received April 13, 2003

* Scientific Center for Nonlinear Wave Mechanics and Technology, Russian Academy of Sciences, ul. Bardina 4, Moscow, 117334 Russia** Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 117977 Russia

226

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Nos. 4–6

2003

GANIEV

et al

.

pocket, and expressions for estimating the frequenciesand amplitudes of vibrations were presented.

It is noteworthy that the structural-mechanical fac-tor not only characterizes the stability of a disperse sys-tem but also can determine kinetic features of polymer-ization. An example of this is emulsion polymerizationin microdrops, which can be regarded as polymeriza-tion microreactors. A similar mechanism is also charac-teristic of the so-called seed polymerization [6]. Pre-liminary experiments demonstrated that wave treat-ment of disperse systems based on some monomers(butyl acrylate, butyl acrylate–acrylic acid) in the pres-ence of various surfactants noticeably (by more than anorder of magnitude) increases the stability of mono-mer–water emulsions and initiates polymerization insuch systems. This enables one to consider such anintense mechanical treatment as a method for control-ling polymerization in kinetically heterogeneous zones[7]. Among mechanical (physical) methods of stimula-

tion of chemical reactions [8] is a method that abruptlyincreases the rates of some solid-phase reactions byshear deformation of the system [9]. In liquid-phasechemical engineering processes, mass transfer can beaccompanied by interfacial instability induced byhydrodynamic and hydrochemical [10] interactions.

The role of shear strain in processes of treatment ofpolymer composites with mixing equipment of varioustypes was revealed by analyzing mathematical modelsof multiphase media and their dynamics in these pro-cesses [11]. The fact that the corresponding equationsof motion involve a term describing the shear stress andstrain allows one to evaluate the processes under inves-tigation in a single context. Such a term is naturallydecisive in estimating the efficiency of mixing viscousmedia in roller mixers, extruders, and so on [11, 12]. Ananalysis of the generalized parameters of activatingmixing of multiphase media containing the liquid phasein a rotary pulsed apparatus also took into account theshear stress and strain [13]. It was noted [14] that appli-cation of vibrations of sufficiently small amplitude to asteady shear flow has virtually no effect on the averagevalues of the normal and tangential stresses. In the non-linear region of the steady shear flow, the dynamic char-acteristics depend not only on the shear vibration fre-quency but also on the steady shear rate: the dynamicviscosity

η

'

and the modulus of elasticity

G

'

decreasewith increasing . Thus, the vibration mixing occur-ring in a polymer system affected by large-amplitudelow-frequency shear vibrations in narrow gaps (

h

!

λ

)can be purposefully used to provide additional mixingand dispersion of polymer composites during mixing(in roller mixers, screw mixers, etc.) or during process-ing of polymer composites into finished products (inextruders, molding machines, calenders, etc.). It ischaracteristic that, for example, a single-screwextruder, according to the principle of its operation, isclassified as a screw pump, in which the flow is laminarbecause of high viscosity [12].

With allowance made for the noted features of theproperties of polymer composites (including the possi-bility of interfacial phenomena) and also for currentconcepts of designing polymer composites, which pro-vide for not only enhancement of their treatment butalso specify combination of their different stages in

γ̇

Kinetics of sedimentation of the filler (zeolite) in compos-ites: (

1

) latex AK-234 + zeolite + 2% starch solution,(

2

) latex AK-234 + zeolite + 1% surfactant (OS-20) solu-tion, (

3

) latex AK-234 + zeolite + 4% surfactant (OS-20)solution, (

4

) latex AK-234 + zeolite + 8% surfactant(OS-20) solution, (

5

) composite

1

after vibration treatment,and (

6

) composite

2

after vibration treatment. Compositions

1

−

4

are obtained by mechanical mixing for 10 min at60 rpm.

Table 1.

Resistance to aggregation for paints at different vi-bration treatment times

Material

Time before onset of sedimentation (h) after vibration treatment for (min)

–* 5 10 15 30

Nitrocellulose enamel NTs-132

2 18 35 50 72

Nitrocellulose enamel NTs-256

3 20 37 48 73

Chalk paste (chalk MTD and water)

1 No sedimentationfor several months

* After mechanical mixing for 10 min at 60 rpm.

Table 2.

Properties of paint coatings at different vibrationtreatment times

Material, propertyTreatment time, min

– 10 20 30

Primer paint GF-0163

Adhesive strength(peeling method), N/m

0.079 0.120 0.215 0.290

Latex paint KCh-132

Particle size,

µ

m 90 65 49 38

0.5 1.0 1.5 2.0 2.5 3.0 3.5

20

0

40

60

80

100

120

Time, h

Sediment, %

1 2 34

56

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SOME FEATURES OF THE DESIGN OF THE PROPERTIES OF POLYMER COMPOSITES 227

order to reduce the number of operations (chemicalmolding, dynamic vulcanization, etc.), for furtherdevelopment of these principles in solving the problemunder discussion, there are grounds to apply an inte-grated approach involving mathematical and physicalmodels of multiphase systems and processes of theirproduction and treatment, including the mechanochem-istry of mixing; structural and other modern physico-chemical methods of analysis; and estimation of thecolloid-chemical properties of a system characterizingits stability. The diversity of mechanochemical phe-nomena occurring during deformation and treatment ofpolymers is largely due to the diversity of mechanicalforces causing these processes. For example, in amechanical field emerging in treatment of viscousmedia (of dynamic viscosity ~10

5

(N s)/m

2

(10

6

P) andhigher at Reynolds numbers Re < 1) in roller, screw,and rotary mixers, mechanochemical processes can beinitiated under mechanical action by mainly shearforces. According to the theory of vibrations and stabil-ity of motion of multiphase media, vibration mixing ofless viscous media involves wave phenomena and theinteraction between forces of vibration and nonvibra-tion nature [15].

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